Currently, standards committee IEEE 802.21 conducts intensive research into the international standards associated with media independent handover (MIH) between heterogeneous networks. MIH provides not only a seamless handover but also a service continuity between the heterogeneous networks, resulting in greater convenience for a user carrying a mobile terminal. IEEE 802.21 defines a variety of functions (e.g., an MIH function, an event trigger function, and an information service (IS) function) as basic requirements.
A mobile subscriber station (MSS) is indicative of a multi-mode node for supporting at least two interface types. The above-mentioned interface type may be determined to be one of a wired interface type (also called a wire-line interface type) such as the Ethernet based on an IEEE 802.3 standard specification, a wireless interface type based on IEEE 802.XX standard specifications (e.g., IEEE 802.11, IEEE 802.15, and IEEE 802.16), and other interface types defined by a cellular standardization organization (e.g., 3GPP or 3GPP2). However, it should be noted that the aforementioned interface types are not limited to the aforementioned wired interface type, wireless interface types, and other interface types, and are applicable to other examples as necessary.
A general Media Independent Handover Function (MIHF) reference model is depicted in FIG. 1. In the figure, MIHF architecture for interaction with other layers and with the remote MIHG is illustrated. In order for the MIHF to provide asynchronous and synchronous services to lower layers and higher layers, Service Access Points (SAPs) such as MIH_MGMT_SAP, MIH_SME_SAP and MIH_SAP along with primitives are defined. MIH_MGMT_SAP defines the interface between the MIHF and the management plane (Management Entity) of different network interfaces and is used for transporting MIH protocol messages between the MIHF and local link layer entities as well as peer MIHF entities. MIH_SAP defines the interface between the MIHF and higher layer entities such as device manager, handover policy control function, transport, layer 3 (L3) mobility management protocol, etc., and is used for MIH configuration and operation. MIH_SME_SAP defines the interface between the MIHF and the Station Management Entity or the Network Management System, and is used for MIG configuration and operation.
FIG. 2 is a structural diagram illustrating a protocol layer of a multi-mode mobile terminal (also called a multi-mode MSS). Referring to FIG. 2, the multi-mode mobile terminal includes a physical (PHY) layer and a Medium Access Control (MAC) layer for individual modes, and locates a Media Independent Handover (MIH) layer under an Internet Protocol (IP) layer.
Media Independent Handover (MIH) must be defined between IEEE 802-series interfaces or between an IEEE 802-series interface and a non-IEEE 802-series interface, such as the aforementioned interface type defined by a cellular standardization organization (e.g., 3GPP and 3GPP2). Also, a protocol for supporting mobility of upper layers such as a mobile IP and a Session Initiation Protocol (SIP) must be supported for a handover function and continuity of services.
The MIH function is located under the IP layer, and facilitates a handover process using input values (e.g., a trigger event and information associated with other networks) received from a second layer (Layer 2). The MIH function may include a plurality of input values based on both user policy and configuration which may affect the handover process. General interfaces among the mobile IP, a third layer (Layer 3) entity such as an SIP (Session Initiation Protocol), and the MIH layer are defined. In this case, the aforementioned interfaces provide the first layer (i.e., the physical layer), the second layer (i.e., the MAC layer), and mobility management information. The MIH function acquires information associated with a lower layer and a network using event and information service (IS) functions.
An upper layer includes an upper management entity for monitoring states and operations of various links contained in a mobile terminal, such that it performs a handover control function and a device manager function. In this case, the handover control function and the device manager may be located at different locations independent of each other, or the handover control function and the device manager may be included as the upper management entities in the upper layer.
FIG. 3 shows a mobile terminal function entity including the MIH function, a network function entity, and a transmission protocol. Dotted lines of FIG. 3 are indicative of primitive information and an event trigger, for example.
In order to quickly perform a handover function, a network layer must use information generated from a link layer, such that the network layer can quickly re-establish a connection state. The link layer event is adapted to predict the movement of a user, and helps a mobile terminal and a network prepare the handover function.
A trigger for the handover may be initiated from the physical (PHY) layer and the MAC layer. A source of the trigger may be a local stack or a remote stack. FIG. 4 is a block diagram illustrating a trigger model.
An event trigger provides state information of a current signal, state change information of another network, and future predicted change information. The event trigger also includes change information of the physical and MAC layers or attribute change information of a specific network.
The event types can be classified into a physical (PHY) layer event, a MAC layer event, a management event, a third layer (L3) event, and an application event, for example. The basic trigger events will hereinafter be described.
A “Link_Up” event occurs when a second layer (L2) connection is established on a specific link interface and an upper layer is able to transmit third layer (L3) packets. In this case, it is determined that all L2 layers contained in a link have been completely configured. A source of the “Link_Up” event corresponds to a “Local MAC” and a “Remote MAC”. The following Table 1 shows parameters of the “Link_Up” event.
TABLE 1NameTypeDescriptionEventSourceEVENT_LAYER_TYPESource at whichevent occursEventDestinationEVENT_LAYER_TYPEDestination towhich event is tobe transmittedMacMobileTerminalMAC AddressMAC address ofMobile TerminalMacOldAccessRouterMAC AddressMAC address ofold access routerMacNewAccessRouterMAC AddressMAC address ofnew access routerNetworkIdentifierMedia SpecificNetwork ID usedfor detectingsubnet change
A “Link_Down” event occurs when the L2 connection is released on a specific interface and L3 packets cannot be transmitted to a destination. A source of the “Link_Down” event is indicative of a local MAC. The following Table 2 shows parameters of the “Link_Down” event.
TABLE 2NameTypeDescriptionEventSourceEVENT_LAYER_TYPESource at whichevent occursEventDestinationEVENT_LAYER_TYPEDestination to whichevent is to betransmittedMacMobileTerminalMAC AddressMAC address ofMobile TerminalMacOldAccessRouterMAC AddressMAC address of oldaccess routerReasonCodeReason for releasedlink
A “Link_Going_Down” event occurs when it is expected that the L2 connection will enter a “Link_Down” state within a predetermined time, and may serve as a signal for initializing a handover procedure. A source of the “Link_Going_Down” corresponds to a “Local MAC” and a “Remote MAC”. The following Table 3 shows parameters of the “Link_Going_Down” event.
TABLE 3NameTypeDescriptionEventSourceEVENT_LAYER_TYPESource at whichevent occursEventDestinationEVENT_LAYER_TYPEDestination to whichevent is to betransmittedMacMobileTerminalMAC AddressMAC address ofMobile TerminalMacOldAccessRouterMAC AddressMAC address of oldaccess routerMacNewAccessRouterMAC AddressMAC address ofnew access routerTimeIntervalTime in msecsPredictedLink_Downtime of linkConfidenceLevel%Link_Down levelpredicted at specifictimeUniqueEventIdentifierUse in eventrollback occurrence
A “Link_Going_Up” event occurs when it is expected that the L2 connection will enter a “Link_Up” state within a predetermined time, and is used when a long period of time is consumed to initialize a network. A source of the “Link_Going_Up” event corresponds to a “Local MAC” and a “Remote MAC”. The following Table 4 shows parameters of the “Link_Going_Up” event.
TABLE 4NameTypeDescriptionEventSourceEVENT_LAYER_TYPESource at whichevent occursEventDestinationEVENT_LAYER_TYPEDestination towhich event isto betransmittedMacMobileTerminalMAC AddressMAC address ofMobile TerminalMacNewAccessRouterMAC AddressMAC address ofnew accessrouterTimeIntervalTime in msecsPredictedLink_UP time oflinkConfidenceLevel%Link_UP levelpredicted atspecific timeUniqueEventIdentifierUse in eventrollbackoccurrence
A “Link_Event_Rollback” event is formed by combining the “Link_Going_Down” event with the “Link_Going_Up” event. The “Link_Event_Rollback” event is indicative of a trigger generated when it is expected that the “Link_UP” event or “Link_Down” event will not be generated any more within a specific time on the condition that the “Link_Going_Up” event or “Link_Going_Down” event are transmitted to a destination. A source of the “Link_Event_Rollback” event corresponds to a “Local MAC” and a “Remote MAC”. The following Table 5 shows parameters of the “Link_Event_Rollback” event.
TABLE 5NameTypeDescriptionEventSourceEVENT_LAYER_TYPESource at whichevent occursEventDestinationEVENT_LAYER_TYPEDestination towhich event is tobe transmittedMacMobileTerminalMAC AddressMAC address ofMobile TerminalMacNewAccessRouterMAC AddressMAC address ofnew access routerUniqueEventIdentifierUse in eventrollbackoccurrence
A “Link_Available” event is indicative of an available state of a new specific link, and indicates the possibility of allowing a new base station (BS) or a new Point of Attachment (POA) to provide a link superior in quality as compared to a current BS or a current POA to which a current mobile terminal is connected. A source of the “Link_Available” event corresponds to a “Local MAC” and a “Remote MAC”. The following Table 6 shows parameters of the “Link_Available” event.
TABLE 6NameTypeDescriptionEventSourceEVENT_LAYER_TYPESource atwhich eventoccursEventDestinationEVENT_LAYER_TYPEDestination towhich event isto betransmittedMacMobileTerminalMAC AddressMAC address ofMobileTerminalMacNewAccessRouterMAC AddressMAC address ofnew accessrouterMacOldAccessRouterMAC AddressMAC address ofold accessrouter
A “Link_Parameter_Change” event is indicative of an event generated when a change of a link parameter value is higher than a specific threshold level. The “Link_Parameter_Change” event includes link layer parameters, for example, a link speed (i.e., a link rate), a QoS (Quality of Service), and an encrypted value, etc. A source of the “Link_Parameter_Change” event corresponds to a “Local MAC” and a “Remote MAC”. The following Table 7 shows parameters of the “Link_Parameter_Change” event.
TABLE 7NameTypeDescriptionEventSourceEVENT_LAYER_TYPESource atwhich eventoccursEventDestinationEVENT_LAYER_TYPEDestinationto which eventis to betransmittedMacMobileTerminalMAC AddressMAC addressof MobileTerminalMacAccessRouterMAC AddressMAC addressof newaccess routeroldValueOfLinkParameterOld value oflink parametersnewValueOfLinkParameterNew value oflink parameters
FIG. 5 exemplarily shows triggers generated until a new link is established when a quality of a current access link is deteriorated.
An information service provides detailed information associated with a network required for both network discovery and network selection, and must be designed to be freely accessed by a user over any network. The information service must include a variety of information components, for example, a link access parameter, a security mechanism, a neighborhood map, a location, information indicative of a service provider and other access information, and a link cost (i.e., cost of link).
The MAC layer of a link interface to which the multi-mode mobile terminal is connected transmits the “Link_Going_Down” trigger to the MIH when a signal quality of the currently connected link is deteriorated, and then performs a scanning process to determine the presence or absence of an accessible link in a homogeneous network. If the accessible link is not detected from the homogeneous network, the mobile terminal must perform the scanning process to determine the presence or absence of the accessible link in a heterogeneous network, but associated prior arts for the aforementioned scanning process have not yet been developed, such that a handover function between heterogeneous networks for the multi-mode mobile terminal cannot be effectively supported.